Squalene promotes cholesterol homeostasis in macrophage and hepatocyte cells via activation of liver X receptor (LXR) [alpha] and [beta]

Objective To examine the effect of squalene on liver X receptors (LXRs) that regulate target genes associated with reverse cholesterol transport and thus control whole-body cholesterol homeostasis. Results To examine the effect of squalene on liver X receptors (LXRs) that regulate target genes associated with reverse cholesterol transport and thus control whole-body cholesterol homeostasis. Squalene significantly stimulated the transactivation of liver X receptor modulator LXR[alpha] and LXR[beta]. The mRNA expression of LXRs and their target genes, including ABCA1, ABCG1 and ApoE, was significantly induced in macrophages stimulated with squalene, resulting in removal of cholesterol from the cells. Notably, squalene did not induce higher hepatic triacylglycerol levels nor did it alter expression of sterol regulatory element-binding protein 1c (SREBP-1c) and FAS in hepatocyte cells, primarily because of its upregulation of Insig-2a, which delays nuclear translocation of SREBP-1c, a key hepatic lipogenic transcription factor. Conclusion Squalene has hypocholesterolemic effect through the activation of LXR[alpha] and [beta] without inducing hepatic lipogenesis.